This invention relates to ultrasonic transducers in general and more particularly to an ultrasonic transducer arrangement which includes ultrasonic oscillators having associated electronic delay chains.
A multiplicity of transducer elements which can be excited differently as to phase and amplitude by means of electronic control members are used in a known transducer arrangement. By changing the amplitude and phase drive of these so-called phased arrays, the radiated and received sound field can be influenced so that angle testing heads and focusing heads can be replaced by a single array test head. The linear propagation time delay of the ultrasound pulses provides tilting, and, through symmetrical, for instance, square law delay of the ultrasound pulses, focusing of the sound field is obtained. By superimposing a linear and a square law delay, the sound field is focused as well as tilted in the longitudinal direction of the transducer arrangement. With an adapter section acting as an acoustical lens, the sound field can additionally be focused in the plane transverse to the longitudinal direction of the transducer arrangement. Focusing is limited to a value, however, which is given by the curvature of the lens (U.S. Pat. No. 3,936,791).
Ultrasonic transducer arrangements with transducer elements in the form of a matrix for producing sectional images of a body to be examined with ultrasound, so-called B-displays are already known (German Pat. No. 28 29 570).
Also known are ring arrays, in which ring shaped ultrasonic oscillators are controlled independently of each other and the aperture angle is changed by adding or disconnecting outer rings and the so-called natural focal point is thereby displaced when transmitting. A so-called breathing aperture is obtained. For receiving, a dynamic focal point, the depth of which can be changed continuously, is generated by continuous electronic phase control. This dynamic focusing, however, requires a relatively large amount of electronics ("Ultrasonic Imaging," vol. 1, no. 1, 1979, pages 56 to 75).